Spinal implant configured for lateral insertion

ABSTRACT

The embodiments provide a spinal implant that is configured for lateral insertion into a patient&#39;s intervertebral disc space. The spinal implant may have a body having a tapered anterior portion and one or more apertures. The tapered anterior portion allows for concomitant distraction of soft tissue during insertion of the implant. In addition, at least some of the apertures are designed to permit a predetermined amount of nutation by a fixation element. The fixations elements that allow nutation enable the fixation element to toggle from one position to another, for example, during subsidence of the implant in situ.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/941,193, filed Nov. 8, 2010 (allowed), which claims benefit of U.S.Provisional Application No. 61/259,401, filed Nov. 9, 2009, and entitled“SPINAL IMPLANT CONFIGURED FOR LATERAL INSERTION,” the entire contentsof which are incorporated herein by reference.

FIELD

The present disclosure relates to orthopedic implants, and moreparticularly to spinal implants that facilitate fusion of bone segmentsand associated methods. Even more particularly, the present disclosurerelates to a spinal fusion implant configured for lateral insertion.

BACKGROUND

The integrity of the spine, including its subcomponents like thevertebral bodies and intervertebral discs that are well known structuralbody parts forming the spine, is key to a patient's health. These partsmay become crushed or damaged as a result of trauma or injury, ordamaged by disease (e.g., by tumor, autoimmune disease), or as a resultof wear over time or degeneration caused by the normal aging process.

In many instances, one or more damaged structural body parts can berepaired or replaced with a prosthesis or implant. For example, specificto the spine, one method of repair is to remove the damaged vertebra (inwhole or in part) and/or the damaged disc (in whole or in part) andreplace it with an implant or prosthesis. In some cases, it is necessaryto stabilize a weakened or damaged spinal region by reducing orinhibiting mobility in the area to avoid further progression of thedamage and/or to reduce or alleviate pain caused by the damage orinjury. In other cases, it is desirable to join together the damagedvertebrae and/or induce healing of the vertebrae. Accordingly, animplant or prosthesis may be configured to facilitate fusion between twoadjacent vertebrae. The implant or prosthesis may be placed withoutattachment means or fastened in position between adjacent structuralbody parts (e.g., adjacent vertebral bodies).

Typically, an implant or prosthesis is secured directly to a bonestructure by mechanical or biological means. One manner of spine repairinvolves attaching a fusion implant or prosthesis to adjacent vertebralbodies using a fixation element, such as a screw. Most implants andtheir attachment means are configured to provide an immediate, rigidfixation of the implant to the implantation site. Unfortunately, afterimplantation the implants tend to subside, or settle, into thesurrounding environment as the patient's weight is exerted upon theimplant. In some cases, this subsidence may cause the rigidly fixedattachment means to either loosen, dislodge or potentially damage one ormore of the vertebral bodies.

Several known surgical techniques can be used to implant a spinalprosthesis. The suitability of any particular technique may depend uponthe amount of access available to the implant site. For instance, asurgeon may elect a particular entry pathway depending on the size ofthe patient or the condition of the patient's spine such as where atumor, scar tissue, or other obstacle is present. Other times, it may bedesirable to minimize intrusion into the patient's musculature andassociated ligamentous tissue. In some patients who have had priorsurgeries, implants or fixation elements may have already been insertedinto the patient's spine and as such, an implant introduction pathwaymay have to account for these prior existing conditions.

Thus, it is desirable to provide an implant that can be easily insertedin accordance with a specific pathway or approach. For example, incertain situations, it is desirable to provide a spinal implant that canbe inserted using a lateral approach. It is further desirable to providean implant that is configured to reduce insertion forces. In addition,it is desirable to provide an implant and associated fixation elementsthat can account for subsidence that occurs with the implant subsequentto implantation while also providing rigid fixation.

Although the following discussion focuses on spinal implants orprostheses, it will be appreciated that many of the principles mayequally be applied to other structural body parts within a human oranimal body.

SUMMARY

The present disclosure describes a spinal implant that is configured forlateral insertion into a patient's intervertebral disc space. Inaccordance with one exemplary embodiment, a spinal implant is providedhaving an upper surface, a lower surface, an anterior portion, aposterior portion and one or more apertures within the posterior portionfor receiving at least one fixation element wherein the implant isconfigured for lateral insertion. For example, the anterior portion orleading edge of the implant may include a sharp, bullet shaped nose ortip. All or some of the apertures may be configured to permit apredetermined amount of nutation by a fixation element, thus allowingthe fixation element to toggle from one position to another. The spinalimplant may additionally include anti-migration features.

In one embodiment, a spinal implant comprises a body and one or moreapertures. The body may comprise an upper surface, a lower surface, atapered anterior portion, and a posterior portion, wherein the body isconfigured for lateral insertion between vertebral bodies of a patient'sspine. The one or more apertures may be provided within the posteriorportion of the body and can receive at least one fixation element. Atleast one of the apertures is configured to permit a predeterminedamount of nutation by a fixation element.

In another embodiment, a method of treating a patient's spine comprisesaccessing at least a portion of a patient's spine via a lateralapproach. A spinal implant is then inserted between vertebral bodies ofthe patient's spine, wherein the spinal implant comprises a body havingan upper surface, a lower surface, a tapered anterior portion, aposterior portion, wherein the body is configured for lateral insertionbetween vertebral bodies of a patient's spine, the implant furtherincluding one or more apertures within the posterior portion of the bodyfor receiving at least one fixation element, and wherein at least one ofthe apertures is configured to permit a predetermined amount of nutationby a fixation element. The spinal implant is attached with the at leastone fixation elements to the vertebral bodies and a predetermined amountof toggling of the fixation element is permitted based on nutation ofthe fixation element during subsidence of the spinal implant.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the disclosure. Additional features of thedisclosure will be set forth in part in the description which follows ormay be learned by practice of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thedisclosure and together with the description, serve to explain theprinciples of the disclosure.

FIG. 1 illustrates a partial cutaway view of a spinal implant of thepresent disclosure in situ.

FIG. 2A illustrates a superior view of the spinal implant of FIG. 1 withfixation screws.

FIG. 2B illustrates a sagittal view of the spinal implant of FIG. 1 withfixation screws.

FIG. 2C illustrates a posterior view of the spinal implant of FIG. 1with fixation screws.

FIG. 2D illustrates a perspective view of the spinal implant of FIG. 1with fixation screws.

FIG. 3 illustrates an enlarged perspective view of an exemplary fixationscrew with locking ring of the present disclosure.

FIG. 4 illustrates a partial cutaway view of the spinal implant of FIG.1 with the fixation screws and locking rings of FIG. 3.

FIG. 5 illustrates a cross-sectional view of the spinal implant withfixation screws of FIG. 4.

FIG. 6A illustrates a perspective view of an alternative embodiment of aspinal implant of the present disclosure with fixation screws.

FIG. 6B illustrates another perspective view of the spinal implant andfixation screws of FIG. 6A.

FIG. 7 illustrates an exemplary embodiment of an imaging marker of thepresent disclosure.

DESCRIPTION OF THE EMBODIMENTS

Referring now to FIG. 1, a spinal implant 10 of the present disclosureis shown. The spinal implant 10 may be implanted in the intervertebralspace 6 between vertebral bodies 2, 4 and secured to the vertebralbodies 2, 4 with fixation screws 40. The spinal implant 10 may beemployed in the lumbar or thoracic regions. Alternatively, the spinalimplant 10 may be employed in the cervical region of the spine, in amanner similar to the one described for the cervical implant of U.S.patent application Ser. No. 11/938,476 filed Nov. 12, 2007, entitled“Orthopaedic Implants and Prostheses,” which is herein incorporated byreference in its entirety. A cervical version may be provided so long asit is appropriately sized and configured, and the surgical approachtakes into account this specific design.

As shown in FIGS. 2A-2D, the spinal implant 10 may include anterior andposterior portions 12, 14 and upper and lower surfaces 16, 18 profiledto correspond with the profile of any bone material to which they are tobe secured. A pair of sidewalls 20 extends between the upper and lowersurfaces 16, 18 and connects to the anterior and posterior portions 12,14. The spinal implant 10 may include a central opening or lumen 24extending between the upper and lower surfaces 16, 18 to facilitate bonyingrowth or fusion between adjacent bone segments, such as vertebralbodies 2, 4. If so desired, the opening 24 may be used to receive andhold bone graft material.

To facilitate ease of insertion, the anterior portion, or leading end 12may be tapered or otherwise shaped for concomitant distraction of softtissue during insertion. For example, the anterior portion 12 may be asharp, bullet shaped nose or tip 22. The unique geometry of the implant10 including this sharpened tip 22 supports reduced insertion forces,and may also help to separate tissue during the insertion. This can behelpful, for example, where scar tissue or other obstructions arepresent at the implantation site, or where there is stenosis and/or someother anatomic anomaly such as where the endplates have grown together.

The posterior portion, or trailing end 14 of the spinal implant 10includes holes 26 for receiving fixation elements, such as bone screws40. In the embodiment shown, the spinal implant 10 includes two screwholes 26, one extending superiorly and one extending inferiorly (see inparticular FIG. 2D). However, one skilled in the art will appreciatethat the implant 10 may comprise any number of holes in any location onthe implant 10. For example, instead of having one superior hole and oneinferior hole in the implant 10 as shown in the drawings, the implantmay have two superior holes, or may be adapted to have two inferiorholes. As previously discussed, the implant 10 may be configured withany number of holes without departing from the spirit of the disclosure.In addition, the implant 10 may include bores 50 for receiving featureslike a radiologic marker or other imaging marker 70, as shown in FIG. 7.The imaging marker 70 may be rod-shaped, for example, for insertion intothe bores 50.

The holes 26 provide a path through which securing means (e.g., fixationelements such as bone screws 40) may be inserted so as to secure theimplant 10 to respective superior and inferior vertebral bodies 2, 4.The holes 26 may be configured to accommodate a variety of securingmeans, such as screws, pins, staples, or any other suitable fasteningdevice. In one embodiment, the fixation screws 40 may be self-tappingand/or self-drilling and may be of a bone-screw-type, such as those wellknown to skilled artisans. In some embodiments, the head portion 42 ofthe fixation screws 40 extends into an elongate body 44 that terminatesat a tip 46. While the implant 10 is shown with screws 40 sized andshaped for unicortical bone fixation, it is contemplated that bonescrews sized and shaped for bicortical bone fixation may also beemployed with the present disclosure.

The holes 26 of the spinal implant 10 may be configured to permit apredetermined amount of screw toggle (i.e., angular skew) and enable alag effect when the fixation screw 40 is inserted and resides inside thehole or lumen 26. In other words, the holes 26 permit a certain degreeof nutation by the screw 40 and thus the screws 40 may toggle from oneposition to one or more different positions, for instance, duringsubsidence. As depicted in FIG. 5, the holes 26 may be configured with aconical range of motion (i.e., angular clearance) of about 25 to about35 degrees, although it is contemplated that an even larger range may bepossible such as 20 to 40 degrees, or 15 to 45 degrees. In oneembodiment, the range is about 22 to 28 degrees. It is also believedthat the predetermined screw toggle (permitted by the clearance betweenthe lumen, or hole 26 and the screw 40) promotes locking of the screw 40to the implant 10 after subsidence subsequent to implantation.Alternatively, the holes 26 of implant 10 may be configured with littleor no clearance to achieve rigid fixation, for example, when implant 10is to be implanted into sclerotic bone.

As shown in FIG. 2C, the spinal implant 10 may have non-parallel upperand lower surfaces 16, 18 to form a wedge-shaped implant 10. However,one skilled in the art will appreciate that the spinal implant 10 mayalso be provided with parallel upper and lower surfaces 16, 18. Thespinal implant 10 may have any suitable shape or size to allow it to beused under lodortic or kyphotic conditions. For instance, in oneexample, the spinal implant 10 may have a 12 degree lodortic profilefrom an anterior-posterior (A-P) view.

In some situations, after insertion into the vertebral body, thefixation element or screw 40 may work itself loose and/or back out,i.e., withdraw from the vertebral body. The consequence of back out orloosening includes improper or incomplete fusion, loss of stability,potential risk to the patient, and a separate costly and often painfulrevision surgery. FIG. 3 shows a fixation screw 40 of the presentdisclosure, along with an anti-backout element to avoid such problems.As illustrated, the anti-backout element comprises a split ring 60 thatacts like a locking ring. FIG. 4 shows the split ring 60 residingbetween the head 42 of the fixation screw 40 and the hole 26 of thespinal implant 10.

The spinal implant 10 and its components may be formed of any suitablemedical grade material, such as biocompatible metals like stainlesssteel, titanium, titanium alloys, etc. or a medical grade plastic suchas polyetheretherketone (PEEK) or another radiolucent material, ultrahigh molecular weight polyethylene (UHMWPE), etc. If so desired, theimplant 10 may also be formed of a bioresorbable material. Thebioresorbable material may preferably be osteoconductive orosteoinductive (or both).

In one exemplary method of inserting the spinal implant 10, the surgeonprepares the implantation site by removing some disc material from thedisc space 6 between two adjacent vertebrae 2, 4. Because the spinalimplant 10 is configured for lateral insertion (i.e., as opposed tomidline insertion), less disc material needs to be removed toaccommodate the implant 10, which has a slim profile. This provides thebenefit of preserving more of the patient's natural anatomy and morespecifically, preserves the soft tissue and ligament surrounding thesite. The spinal implant 10 may be provided to the surgeon with thescrews 40 pre-attached, or separately, as desired. After the surgeonplaces the implant 10 in the desired location, such as the cervicalregion of a patient's spine, the surgeon can tighten the screws 40 intothe surrounding bone tissue, thereby securing the implant 10.

As noted, the implant 10 may be configured to permit a predeterminedamount of screw toggle and enable a lag effect when the fixation screw40 is inserted and resides inside the hole or lumen 26. Upon tightening,the lag effect may be observed whereby the implant 10 draws bone tissuetowards itself, which may promote better fusion.

As further noted, the predetermined screw toggle promotes locking of thescrew 40 to the implant 10 after subsidence subsequent to implantation.For example, after surgery, the patient's natural movement will resultin settling and subsidence of bone tissue and the implant 10 in situ. Itis believed that during this process, the weight exerted upon theimplant 10 causes the fixation screws 40 to toggle and eventually lockagainst one or more surfaces of the holes 26 of the implant 10.

Some practitioners prefer to allow some degree of movement between theimplant and the adjacent vertebral body after implantation. In that casethe screw heads 42 may be provided with contours on its underside thatallow the screws 40 to toggle with respect to the contoured opening 26of the implant 10. Other practitioners may prefer a more rigid implantthat is firmly locked to the adjacent vertebral body. The embodiments ofimplant 10 allow either preference.

In the rigidly fixed version, the screws 40 may be provided without thecontour on its underside (i.e., a relatively flat underside) while theopening 26 of the implant 10 would likewise not include a contour. Thus,when secured together, the screws 40 and implant 10 form a rigidlylocked construct. Where rigid fixation is desired (i.e., no toggle), theunderside of the screws 40 may also include surfaces features as well inorder to provide secure attachment to the implant 10.

While a toggle and a rigidly fixed version of the implant 10 and screws40 are described, it is understood that a combination of toggling andrigid fixation may be accomplished in a single implant 10. For example,it is possible to provide an implant 10 that allows toggling of one ormore screws 40, while also allowing rigid fixation of the other of thescrews 40.

It will also be appreciated that the angular positioning of the variousholes, as described above, allows the present implant 10 to be of arelatively small size and therefore insertable from a lateral approachwithin the intervertebral spaces of the spine. Thus, it will beappreciated that the angular positioning of the holes is important tothe effective operation of the implant 10 and the ability to “stack”implants in adjacent multilevel procedures without the securing meansinterfering with each other, which can be of major significance in somesituations.

As illustrated, the spinal implant 10 may have any variety of surfacefeatures, such as anti-migration and bone attachment features. Forexample, it is contemplated that the implant may have threads, teeth,barbs, surface roughenings, etc. to assist in bone attachment. Further,biological agents such as bone growth factors, for example, may beemployed to enhance bone attachment. FIGS. 6A and 6B illustrateexemplary embodiments of a spinal implant 10 of the present disclosurehaving teeth 30 on the upper and lower surfaces 16, 18 to preventmigration after implantation and enhance securement to bone tissue.

Other embodiments of the disclosure will be apparent to those skilled inthe art from consideration of the specification and practice of thedisclosure provided herein. It is intended that the specification andexamples be considered as exemplary only.

What is claimed is:
 1. A method of treating a patient's spinecomprising: accessing at least a portion of a patient's spine via alateral approach; inserting a spinal implant between vertebral bodies ofthe patient's spine, wherein the spinal implant comprises a body havingan upper surface, a lower surface, a tapered anterior portion, aposterior portion, wherein the body is configured for lateral insertionbetween vertebral bodies of a patient's spine, the implant furtherincluding one or more apertures within the posterior portion of the bodyfor receiving at least one fixation element, wherein at least one of theapertures is configured to permit a predetermined amount of nutation bya fixation element; attaching the spinal implant with the at least onefixation element to the vertebral bodies; and permitting a predeterminedamount of toggling of the fixation element based on nutation of thefixation element during subsidence of the spinal implant.
 2. The methodof claim 1, wherein the spinal implant comprises one or more bores forreceiving an imaging marker, and further including the step of insertingthe spinal implant based on visual cues provided by the imaging marker.3. The method of claim 1, wherein inserting the spinal implant comprisesinserting the spinal implant based on visual cues provided by aradiopaque imaging marker on an intraoperative image.
 4. The method ofclaim 1, wherein inserting the spinal implant also includes distractingsoft tissue with the tapered anterior portion.